When clothes are dried in a rotary clothes dryer, the tumbling action of the clothes in the dryer drum causes enough friction between the clothes and the interior of the dryer drum to induce appreciable charges of static electricity in the clothes. The static charges cause the clothes to stick to each other when they are removed from the dryer. This makes it difficult to separate the clothes from each other for folding or ironing. In addition, the static charges may cause lint to stick to the clothes and require extensive brushing to remove the lint. The static charges are not known to be harmful to people, but they are troublesome, and it is highly desirable to provide a means of neutralizing the static charges before the clothes are removed from the dryer.
U.S. Pat. No. 2,568,068 discloses one type of prior art anti-static circuit which has been used to neutralize static electric charges on garments in rotary dry cleaning machines. Referring to FIG. 2 of U.S. Pat. No. 2,568,068, the dry cleaner includes a rotatable drum or basket 16 which is rotatably mounted within a housing 15. Housing 15 and drum 16 are both normally filled with dry cleaning fluid during the cleaning operation. The cleaning fluid can flow from the interior of drum 16 to the exterior thereof through perforations 17 therein. The anti-static circuit includes an elongated cylindrical grounding electrode 10 which is mechanically attached to an end of housing 15 and extends axially inwardly outside of drum 16. The static electric charges which collect on garments within a perforated rotary drum 16 are electrically communicated through the dry cleaning fluid and perforations 17 to grounding electrode 10 and thence through an electric conductor 18 to a ground connection 19. A permanent magnet 14 is mounted on the inner end of grounding electode 10 with its magnetic lines of force oriented so as to deflect electric currents in its neighborhood toward the grounding electrode 10 to enhance the anti-static current flow. Here the magnet is shielded by the metal of the rotor so that the magnetic field cannot enter the interior of the dryer. The magnet 14 does not neutralize the static electricity, but rather directs the flow of electrons in its neighborhood toward grounding electrode 10 which performs the neutralizing function.
The construction shown in U.S. Pat. No. 2,568,068 is suitable for use in dry cleaning machines but not in rotary clothes dryers because the latter are not filled with an electrically conductive fluid for transferring the electric charge from the interior of the rotating clothes drun to a stationary grounding electrode outside of the rotating drum.
U.S. Pat. No. 3,161,479 discloses an anti-static circuit which can be used in rotary clothes dryers. Referring to FIGS. 1 and 2 U.S. Pat. No. 3,161,479, this anti-static circuit includes a frictional belt drive unit 30 which operates on the well known Van de Graaff principle for generating a static charge. Frictional belt drive unit 30 is continuously driven by a V-belt drive 40 coupled to dryer motor M. The static charge is developed between a charge deposit brush 31 and a charge pick-up brush 32. Charge deposit brush 31 is grounded through conductor 24 and charge pick-up brush 32 is coupled through conductor 21 to an electrically conductive roller 51 which bears against the end of the rotating clothes dryer drum T. Roller 51 is spring loaded to maintain electrical contact with the periphery of drum T and conveys the electric charge from frictional drive belt unit 30 to drum T. As the clothes tumble, they contact the interior surface of drum T and thus pick up the electric charge therefrom to neutralize the static charge on the clothes. This does not use a magnetic field
Although the above-described anti-static circuit is usable in rotary clothes dryers, it is relatively complex and costly and requires substantial modifications in the dryer's structure.